Multi-section hydraulic ram

ABSTRACT

A three section telescopic hydraulic ram features the ability to have its mid-section and interior or rod section independently actuated. Thus, the mid-section and rod section of the ram may be extended or retracted as a unit relative to the exterior base section, or the mid-section and rod section may move relative to each other in either direction while moving relative to the base section. This capability for individual control of the ram midsection and rod section is achieved through a unique combination of fluid inlet porting and a divided piston construction for the interior or rod section of the ram.

United States Patent Sung 1 1 Oct. 10, 1972 [54] MULTI-SECTION HYDRAULICRAM [72] Inventor: Fu-Tlen Sung, Waynesboro, Pa.

[73] Assignee: Walter Kldde 8: Company, Inc.,

' Clifton, NJ.

[22] Filed: Sept. 28, 1970 [2]] App]. No.: 76,373

[52] [1.8. CI ..92/52 [51] Int. Cl ..F0lb 7/20 [58] Field of Search..92/51, 52, 53, 113

[56] References Cited UNITED STATES PATENTS 3,139,004 6/1964 Haumann..92/52 X 3,464,263 9/1969 Omandam ..92/53 X 3,213,765 10/1965 Knable..92/52 FOREIGN PATENTS OR APPLICATIONS 423,733 4/1941 Italy ..92/52Primary Examiner-Martin P. Schwadron Assistant Examiner-Leslie J. PayneAttorney-Brady, OBoyle & Gates [57] ABSTRACT A three section telescopichydraulic ram features the ability to have its mid-section and interioror rod section independently actuated. Thus, the mid-section and rodsection of the ram may be extended or retracted as a unit relative tothe exterior base section, or the mid-section and rod section may moverelative to each other in either direction while moving relative to thebase section. This capability for individual control of the rammid-section and rod section is achieved through a unique combination offluid inlet porting and a divided piston construction for the interioror rod section 'of the ram.

9 Claims, 1 Drawing Figure PATENTElJunT 10 1912 IN VEN TOR Fu-TIEN suNeer M 0' ATTORNEYS MULTI-SECTION HYDRAULIC RAM The objective of theinvention is to provide a plural section fluid pressure operatedtelescopic ram for numerous applications, such as the operation andcontrol of multi-section telescopic crane booms and the like. Moreparticularly, the ram embodying the invention has fluid passage meansand an effective piston arrangement which renders its mode of operationmore flexible or versatile than known prior art structures for a similarpurpose. In a three section ram incorporating the features of theinvention, the mid-section and the interior section of the ram are fullyindependently operable under power, both with respect to extension andretraction. That is to say, one of these ram sections may be extendingrelative to the fixed base section while the other interior ram sectionis retracting. Also both interior sections may be extended orretractedin unison relative to the base section. The physical construction of theram and its operating fluid circuitry is simplified, entirely practicaland economical.

Other features and advantages of the invention will appear during thecourse of the following description.

BRIEF DESCRIPTION OF DRAWING The drawing FIGURE is a centrallongitudinal vertical section through a three section ram embodying theinvention.

DETAILED DESCRIPTION Referring to the drawing in detail whereinlikenumerals designate like parts, the numeral designates a base or exteriorcylinder or ram section which is normally fixed during operation andconnected with some stable structure. The base section 10 has end caps11 and 12 secured to its opposite ends and closing such ends andpreferably immediately inwardly of these caps spacer rings 13 and 14 aresecured within the bore of the base section to serve as piston stopelements, as will be further described.

A ram mid-section 15 is disposed within the base section 10concentrically and in spaced relation to the base section so as to forman annular fluid chamber 16 between the base and mid-sections. At itsrearward end, the mid-section 15 carries a piston 17 rigid therewithhaving external seals 18 and internal seals 19, the latter engaging aninterior relatively small diameter open-ended fluid inlet tube 20 havingits rearward end anchored securely to the cap 12 of the ram basesection. The tube 20 also assists somewhat in the guidance of the piston17 of the ram mid-section. As will be further explained, the tube 20delivers operating fluid to the piston head of the interior rod sectionof the ram to extend the same.

The interior rod section of the ram is designated by the numeral 21, andthis rod section is disposed concentrically inside of the mid-section 15in spaced relation. The rod section 21 is also concentrically spacedfrom the interior tube 20, the latter being centered on the longitudinalaxis of the ram structure. The mid-section 15 has a forward end cap 22through which the rod section 21 may slide during extension andretraction and a spacer ring 23 is disposed in the bore of themidsection 15 immediately inwardly of the cap 22 to form a limit stopfor the piston head 24 secured to the rear end of the rod section 21.

The piston head 24 forms a unique and important element of the ram inconjunction with a forward end closure cap 25 of the rod section 21which lies ahead of the forward open end of the tube 20 when the ram isfully retracted, as shown in the drawing figure. Another spacer ring 26is disposed within the bore of mid-section 15 immediately ahead of thepiston 17 to serve as a retraction stop for the ram rod section 21 andits piston head 24.

The piston head 24 of rod section 21 slides in the bore of mid-section15 and has external seals 27, as shown. The piston head 24 has a bore 28which concentrically surrounds the tube 20 in spaced relation thereto.It may now be seen that additional working fluid chambers 29 and 30 areformed between the ram sections 15 and 21 and between the section 21 andtube 20.

A fitting 31 is connected in the base section 10 near the rear end cap12 to admit working fluid to the extension side of the mid-sectionpiston 17. A like fitting 32 connected in the base section 10 marksforward end admits fluid to the chamber 16 and the retraction side ofthe mid-section piston 17. Another fitting 33 connected into themid-section 15 near its forward end ports fluid into the chamber 29 andthe retraction side of rod section piston 24. As previously stated, thetube 20 from its rear end ports working fluid into the annular chamber30 and to the extension side of the piston 24, as shown by the arrows inthe drawing figure.

With respect to the operation of the rod section piston 24, thefollowing should be explained, making reference to the letterdesignations in the drawing figure. The effective area of the rodsection piston 24 is actually the sum of the areas (A) plus (B). Theeffect is the same as if the piston head 24 were a full solid pistonhead including the areas occupied by the tube 20 and the fluid passagethrough the bore 28. In effect, the working area of the piston head 24is split or divided between the area (B) of the piston head and thedownstream area (A) of the cap 25. This can be seen from the fact thatthe fluid pressure (P) is the same in all directions. The area (D) isequal to the area (B) (C) on piston head 24. The forces acting on thearea (B) (C) on both sides of piston head 24 are equal and cancel eachother. The fluid pressure acting on the area (D) at the rod section endwill be equal to, but in opposite direction, to the pressure acting onthe area (B) (C) on piston 17. The net effect is, therefore, that theforce acting on the rod end cap 25 is equal to the pressure (P) timesthe area (A) (D). However, on the rear face of piston head 24, there isstill the area (C) subject to fluid pressure (P). Therefore, if thefluid pressure (P between ram sections 15 and 21 is equal to zero, thenthe actual force acting on the rod section is (P) times the total area(A) (D) (C). But if (P,) is not zero, there will be a force (P times (E)in the opposite direction. The net result will then be P [(A) (D) (C) P,(E). By controlling the pressures (P), (P (P and (P in conjunction withthe various areas, one can either extend one section 15 or 21 of the ramat a time or extend both sections simultaneously. In the latter case,one can also control the relative speeds of extension of the sections 15and 21. With the right combination, it is possible to extend the twosections at the same speed.

The structure permits varying of the volume and pressure of the workingfluid entering the ports 31 and 20 to control the displacement of theram mid-section and the rod section 21 individually. Similarly, byvarying the volume and pressure of the fluid entering ports 32 and 33,one can control the amount of retraction of the sections 15 and 21individually. The pressure of the fluid entering the port or tube can bemade different from the pressure entering through the port 31 by usingtwo different pump sections. This will provide better control, althoughby merely varying the fluid volume through a single pump and flowdivider, will provide adequate control on the displacement of the ramsections 15 and 21.

From the above analysis, it may be seen that a three section hydraulicram is provided wherein the two interior sections are individuallycontrollable, both on their extension and retraction strokes. The pistonhead 24 of the interior rod section is bored out in the center toprovide for the tube 20 and surrounding fluid chamber, but taking intoaccount the downstream area (A) on the rod section the net effectivearea of the piston head 24 is the same as though it were a solid pistonhaving the total of the areas (A) and (B).

The structure is simplified and practical to construct in all respects.The spacer elements 14 and 26 serve to positively limit retraction ofthe mid-section l5 and rod section 21, as shown. The spacers l3 and 23in like manner will positively limit the extension stroke of these ramsections.

It is to be understood that the form of the invention herewith shown anddescribed is to be taken as a preferred example of the same, and thatvarious changes in the shape, size and arrangement of parts may beresorted to, without departing from the spirit of the invention or scopeof the subjoined claims.

I claim:

I. A fluid operated extensible and retractable ram comprising a basesection, a mid-section and an interior rod section arranged intelescopic interfitting relation, an annular piston on the mid-sectionadapted to reciprocate in the bore of the base section, an annularpiston on the rod section adapted to reciprocate in the bore of themid-section, a closure element on the end of the rod section distantfrom the rod section piston, a central fluid inlet tube fixed withrelation to the base section and extending axially through the bores ofsaid annular pistons and within the base section to a point close to theclosure element when the ram is in a fully retracted condition, saidannular mid-section piston having its bore in fluid sealing engagementwith the exterior surface of said tube, the annular rod section pistonhaving its bore spaced from said tube to provide a passageway for fluidtherebetween, said tube delivering working fluid to the extension sideof the rod section piston and to the face of said closure element, fluidpassage means for delivering fluid to the retraction side of the rodsection piston, and separate fluid passage means for delivering fluid tothe extension and retraction sides of the mid-section piston, therebyenabling the mid-section and rod section to be independently andindividually operated.

2. The structure as defined in claim 1, and said tube having a length atleast as great as the full stroke of the mid-section piston so that suchpiston always remains engaged with said tube.

. he structure as defined in claim 2, and a closure cap for the rear endof the base section, and the rear end of said tube anchored to theclosure cap and having its bore opening therethrough for the receptionof fluid.

4. A fluid operated extensible and retractable ram comprising a basesection, a mid-section and an interior rod section arranged intelescopic interfitting relation, an annular piston on the mid-sectionadapted to reciprocate in the bore of the base section, an annularpiston on the rod section adapted to reciprocate in the bore of themid-section, a closure element on the end of the rod section distantfrom the rod section piston, a central fluid inlet tube fixed withrelation to the base section and extending axially through the bores ofsaid annular pistons and within the base section to.a point close to theclosure element when the ram is in a fully retracted condition, theannular rod section piston having its bore spaced from said tube toprovide a passageway for fluid therebetween, said tube deliveringworking fluid to the extension side of the rod section piston and to theface of said closure element, fluid passage means comprising a fittingconnected in the side wall of said mid-section near the forward endthereof and forwardly of the base section when the ram is fullyretracted for delivering fluid to the retraction side of the rod sectionpiston, and separate fluid passage means for delivering fluid to theextension and retraction sides of the mid-section piston, therebyenabling the mid-section and rod section to be independently andindividually operated.

5. The structure as defined in claim 4, and said separate fluid passagemeans comprising a pair of fittings connected in the side wall of thebase section near opposite ends of the base section.

6. The structure as defined in claim 1, and said base, mid and rodsections of the ram being in substantially concentric spaced relation toprovide fluid chambers therebetween, and said mid-section and rodsection pistons having their peripheries extending radially beyond thetube members which constitute the midsection and the rod section of theram.

7. The structure as defined in claim 6, and spacer sleeves disposedwithin the bores of the base section and mid-section and engageable bythe pistons of the mid-section and rod section to positively limitretraction and extension thereof.

8. The structure as defined in claim 1, and said interior rod sectionincluding a tubular body, said rod section piston secured to the rearend of the tubular body and extending radially inwardly and outwardlythereof.

9. The structure as defined in claim 1, and the total effectiveextension face of the rod section piston being a divided face andcomprising the sum of the areas of the rear side of the rod sectionpiston and that area of the the closure element which is encompassed bya projection of the bore of the rod section piston.

1. A fluid operated extensible and retractable ram comprising a basesection, a mid-section and an interior rod section arranged intelescopic interfitting relation, an annular piston on the mid-sectionadapted to reciprocate in the bore of the base section, an annularpiston on the rod section adapted to reciprocate in the bore of themid-section, a closure element on the end of the rod section distantfrom the rod section piston, a central fluid inlet tube fixed withrelation to the base section and extending axially through the bores ofsaid annular pistons and within the base section to a point close to theclosure element when the ram is in a fully retracted condition, saidannular mid-section piston having its bore in fluid sealing engagementwith the exterior surface of said tube, the annular rod section pistonhaving its bore spaced from said tube to provide a passageway for fluidtherebetween, said tube delivering working fluid to the extension sideof the rod section piston and to the face of said closure element, fluidpassage means for delivering fluid to the retraction side of the rodsection piston, and separate fluid passage means for delivering fluid tothe extension and retraction sides of the mid-section piston, therebyenabling the mid-section and rod section to be independently andindividually operated.
 2. The structure as defined in claim 1, and saidtube having a length at least as great as the full stroke of themid-section piston so that such piston always remains engaged with saidtube.
 3. The structure as defined in claim 2, and a closure cap for therear end of the base section, and the rear end of said tube anchored tothe closure cap and having its bore opening therethrough for thereception of fluid.
 4. A fluid operated extensible and retractable ramcomprising a base section, a mid-section and an interior rod sectionarranged in telescopic interfitting relation, an annular piston on themid-section adapted to reciprocate in the bore of the base section, anannular piston on the rod section adapted to reciprocate in the bore ofthe mid-section, a closure element on the end of the rod section distantfrom the rod section piston, a central fluid inlet tube fixed withrelation to the base seCtion and extending axially through the bores ofsaid annular pistons and within the base section to a point close to theclosure element when the ram is in a fully retracted condition, theannular rod section piston having its bore spaced from said tube toprovide a passageway for fluid therebetween, said tube deliveringworking fluid to the extension side of the rod section piston and to theface of said closure element, fluid passage means comprising a fittingconnected in the side wall of said mid-section near the forward endthereof and forwardly of the base section when the ram is fullyretracted for delivering fluid to the retraction side of the rod sectionpiston, and separate fluid passage means for delivering fluid to theextension and retraction sides of the mid-section piston, therebyenabling the mid-section and rod section to be independently andindividually operated.
 5. The structure as defined in claim 4, and saidseparate fluid passage means comprising a pair of fittings connected inthe side wall of the base section near opposite ends of the basesection.
 6. The structure as defined in claim 1, and said base, mid androd sections of the ram being in substantially concentric spacedrelation to provide fluid chambers therebetween, and said mid-sectionand rod section pistons having their peripheries extending radiallybeyond the tube members which constitute the mid-section and the rodsection of the ram.
 7. The structure as defined in claim 6, and spacersleeves disposed within the bores of the base section and mid-sectionand engageable by the pistons of the mid-section and rod section topositively limit retraction and extension thereof.
 8. The structure asdefined in claim 1, and said interior rod section including a tubularbody, said rod section piston secured to the rear end of the tubularbody and extending radially inwardly and outwardly thereof.
 9. Thestructure as defined in claim 1, and the total effective extension faceof the rod section piston being a divided face and comprising the sum ofthe areas of the rear side of the rod section piston and that area ofthe the closure element which is encompassed by a projection of the boreof the rod section piston.